Two novel lateral metal-contact radio-frequency microelectromechanical system (RF MEMS) switches are reported. These switches are implemented with quasi-finite ground coplanar waveguide (FGCPW) configuration and actuated by applying electrostatic force on a high-aspect-ratio cantilever beam. It is demonstrated that the insertion loss of the switch is less than 0.2 dB up to 15 GHz and the isolation is higher than 20 dB up to 25 GHz. An RF model of the switches is used to analyse the effects of the switch design parameters and RF performance. The optimization of the switch mechanical design is discussed where the threshold voltage can be lower than 25 V. The lateral switches are fabricated by deep reactive ion etching (DRIE) process on a silicon-on-insulator (SOI) wafer with shadow mask technology.

https://nocweba.ntu.edu.sg/laq_mems/journal%20papers/2005/Low-loss%20lateral%20micromachined%20switches%20with%20frequencies%20from%20DC%20to%2025%20GHz.pdf

Low-loss lateral micromachined switches for high frequency applications

This paper presents the design, fabrication, and measurement results for a novel non-contact-type radio-frequency (RF) microelectromechanical systems switch for 24-GHz radar applications. The proposed switches are free from unavoidable microwelding and stiction problems in other contact types, which in turn guarantee high reliability and long lifetime. The developed switch is a capacitive shunt type using a variation of the capacitance between the signal line and ground lines. The capacitance is precisely regulated by comb-drive actuators. This concept is simple, but the design requires a large and precise mechanical motion. In addition, for a low-loss switch structure, an air bridge with a large air gap is required. Therefore, the selective silicon-on-insulator process, based on the sacrificial bulk micromachining process, is designed for this switch fabrication. First, large insulating supports are fabricated 60 ?m below the wafer surface, and then, the RF switch is fabricated on these insulating supports. The measured actuation voltage is 25 V, and the actuation stroke is 25 ?m. The switching times are 8 ms in the off to the on state and 200 ?s in the on to the off state. In the RF characteristic measurements, the insertion loss without the long coplanar waveguide line loss is 0.29 dB and the isolation is 30.1 dB at 24 GHz. The bandwidth is relatively narrow, and the isolation is 25 dB or better in the range of 23.5-29 GHz. The reliability test for the switch was performed 109 times with 18-mW RF power. We observed no mechanical failure or RF performance degradation. A power handling capacity of 0.9 W with a hot-switch condition was achieved.

A Non-Contact-Type RF MEMS Switch for 24-GHz Radar Applications

Currently, the technology of microelectromechanical systems is widely used in the development of high-frequency and ultrahigh-frequency devices. The most important requirements for modern and advanced devices of the ultra-high-frequency range are the reduction of weight and size characteristics, power consumption with an increase in their functionality, operating frequency and level of integration. Radio frequency microelectromechanical switches are developed using the technology of the manufacture of CMOS-integrated circuits. Integrated radio frequency control circuits require low control voltages, the high ratio of losses to the isolation in the open and closed condition, high performance and reliability. This review is devoted to the analytical approach based on the knowledge of materials, basic performance indices and mechanisms of failure, which can be used in the development of radio-frequency microelectromechanical switches.

https://www.mdpi.com/2079-9292/7/12/415/pdf

Analytical Approach in the Development of RF MEMS Switches

The present authors have earlier reported the employment of varying section fixed-fixed beam for achieving lower pull-in voltage with marginal fall in restoring force. Reducing Young’s modulus also reduces the pull-in voltage but with lesser degree of reduction in restoring force. Composite beams are ideal alternatives to achieve decreased Young’s modulus. Hence new varying section composite fixed-fixed beam type RF MEMS switch has been proposed. The main advantage of this RF MEMS switch is that lower pull-in voltages can be achieved with marginal fall in stiction immunity. Spring constant of the proposed switch has been obtained using simulation studies and it has been shown that the spring constant and therefore the pull-in voltage ( ) can be considerably reduced with the proposed switch. Simulation studies conducted on the proposed switch clearly demonstrate that the pull-in voltage can be reduced by 31.17% when compared to the varying section monolayer polysilicon fixed-fixed beam. Further this approach enables the designer to have more freedom to design lower pull-in voltage switches with improved stiction immunity.

/pdf/low-actuation-voltage-rf-mems-switch-using-varying-section-2opd8tj2jy.pdf

Low Actuation Voltage RF MEMS Switch Using Varying Section Composite Fixed-Fixed Beam

A dc 6 GHz single-pole double-throw (SPDT) switching circuit that employs lateral metal-contact micromachined switches is investigated. The lateral metal-contact switch consists of a set of quasi-finite ground coplanar waveguide (FGCPW) transmission lines and a high-aspect-ratio cantilever beam. A single-pole single-throw (SPST) lateral micromachined switch has an insertion loss of 0.08 dB and a return loss of 32 dB at 5 GHz. The isolation is 32 dB at 5 GHz. The measured insertion loss of the SPDT switching circuit is below 0.75 dB, whereas the return loss is higher than 19 dB at 5 GHz. The isolation at 5 GHz is 33 dB. Pull-in voltage of the switch is 23.3 V and switching time is 35 μs. The size of the SPDT switching circuit is 1.2 mm × 1.5 mm. A main advantage of this circuit structure is simple fabrication process with high yield (>90%) based on the deep reactive ion etching (DRIE) technique of silicon-on-insulator (SOI) wafer and shadow mask technology.

https://nocweba.ntu.edu.sg/laq_mems/journal%20papers/2005/A%20single-pole%20double-throw%20circuit%20using%20lateral%20metal-contact%20micromachined%20switches.pdf

A single-pole double-throw (SPDT) circuit using lateral metal-contact micromachined switches

This paper presents a novel lateral series microwave switch fabricated on a silicon-on-insulator (SOI) substrate with a finite ground coplanar waveguide (FGCPW) configuration which is laterally actuated by the electrostatic force. The switch is built with a cantilever beam in the direction of the signal line and a fixed electrode is located opposite the cantilever beam. The mechanical structures are fabricated using SOI deep reactive ion etching (DRIE) and shadow mask technology. The fabricated lateral RF MEMS switch has an isolation of 16 dB at 20 GHz. The insertion loss of the switch is 1 dB and return loss is 15 dB at 20 GHz. The threshold voltage is 19.2 V and switching time is 30 μs.

https://nocweba.ntu.edu.sg/laq_mems/journal%20papers/2004/A%20new%20approach%20of%20lateral%20RF%20MEMS%20switch.pdf

A New Approach of Lateral RF MEMS Switch

This paper presents a novel type of lateral series microwave switch on a silicon-on-insulator (SOI) substrate with a coplanar waveguide (CPW) configuration. It is built with a cantilever beam at the side of the gap of the microwave t-line and laterally driven by electrostatic force. The mechanical structures are made of single-crystal-silicon and fabricated by deep reactive ion etch (DRIE) technology. Evaporated aluminum serves as contact material. The fabrication process only needs one mask. The measured result shows up to 26.5 GHz the isolation of the switch is over 18 dB. The threshold voltage is about 12 volts.

P. Win

Papers

A New Approach of Lateral RF MEMS Switch

An approach of lateral RF MEMS switch for high performance

A new lateral rf switch using soi-deep-etching fabrication process